The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile machine, and in particular, to a control technology of sheet-feeding in case of feeding a sheet to an image forming section of an image forming apparatus.
In an image-forming apparatus such as a copying machine, a printer and a facsimile machine, a controller is designed so that a plurality of sets of documents representing a plurality of images may be made efficiently. The controller is provided with a continuous interval timer which establishes an interval between each of the sheets in a continuous image forming process appropriately. In addition, the controller controls the operation of the continuous interval timer so that an interval between sets can be set to be different from an interval between sheets.
The control of the continuous interval timer in the above-mentioned continuous image forming process is explained referring to FIG. 1.
In the image forming process, interval xe2x80x9ctxe2x80x9d between images and interval T between sets are formed by a registration roller representing a second sheet-feeder. A sheet fed from each sheet-feeding cassette is stopped at the registration roller temporarily, and the sheet is conveyed to a transfer device after the registration roller starts operating.
Further, the interval xe2x80x9ctxe2x80x9d between images is formed by the logical product of a time formed by the continuous interval timer, information of completion for sheet-feeding preparation and an image-formation synchronization signal.
The time formed by the continuous interval timer is established by the parameters such as a size of sheets and an image-forming mode. Information of completion for sheet-feeding preparation is information showing that a certain period of time has passed from the signal of detection for the leading edge of a sheet generated by the sheet sensor provided right on the upstream-side of the registration roller. Though there is a case that the interval T of sets is formed by the summation of the intervals xe2x80x9ctxe2x80x9d of images for the number of images which constitute each set, there is also a case that the interval formed by the summation of the intervals of images for the number of images is changed by the time for a finishing process, and in this case, considering the time needed for the finishing process, the interval T of sets is formed by adding a correction time to the time formed by the interval timer nxc3x97xe2x80x9ctxe2x80x9d (where n is a number of images constituting one set).
As shown by correction time d1 in FIG. 1(a) and by correction time d2 in FIG. 1(b), the correction time for forming the interval T of sets has different values depending upon the number of images forming one set. Incidentally, a1 and a2 in FIG. 1(a) and FIG. 1(b) show the images constituting a first set, while b1 and b2 show the images constituting a second set.
When the interval T of sets in the continuous image forming process is established by correcting the measured time by the continuous interval timer, there is a problem that a time control by the continuous interval timer becomes extremely complex. That is, the time for establishing the interval of images established by the continuous interval timer itself has various kinds of values depending upon sheet sizes and image forming modes. In addition, the calculation that adds the various correction values concerning the finishing process with respect to the various establishing times and control based on the calculation become complex so that the appropriate condition may fail to be established.
An object of the invention is to solve the above-mentioned problem in the control of the continuous image formation.
The above-mentioned object of the invention is attained by either one of the structures described below.
(1) An image forming apparatus having an image forming section for forming an image on a sheet, a sheet storing section for storing plural sheets, a first sheet-feeder for conveying sheet from the sheet storing section, a second sheet-feeder for receiving a sheet from the first sheet-feeder and for supplying the sheet to the image forming section, a finisher for finishing an image-formed sheet and a controller for controlling sheet-feeding operation of the second sheet-feeder, wherein in the continuous image forming process which makes plural sets of image-formed sheets which are finished by the finisher, the controller controls the starting of the second sheet-feeder that forms the interval of sets based on the logical products of time passing information established by the continuous interval timer that establishes the interval between each sheet, information of completion for sheet-feeding preparation in the second sheet-feeder, image-forming information in the image forming section and information of time passing from the conveyance starting of a first sheet by the second sheet-feeder that is established by the finishing time in the finisher.
(2) A control method of sheet-feeding in an image forming apparatus for supplying a sheet to the image forming section of the image forming apparatus having an image forming section and a finisher which receives the sheet to perform finishing on which an image is formed in the image forming section, wherein in the continuous image forming process that makes a plurality of image-formed sheets, by the logical products of the condition on the image forming process in the image forming apparatus and the condition of operating process in the finisher, the starting of sheet-feeder which supplies the first sheet of the set to the image forming section is controlled.